According to Fighter's Only:

"It is undoubted that I will face Roy Jones. We have talked too much, have signed some contracts and we want to make it the sooner the better. It’s not for money or spotlight, it’s for my desire.  Before that UFC is my focus. Dana treats me very well, as do all the staff of the organization. However I have to search what is better for myself.  The UFC middleweight champion says he is "very satisfied with my results [in the UFC] and I want to continue this way until the end of my contract".

Stating that he will retire when the contract is completed, he explained the thinking behind his decision to Gazeta de Povo.  

"I have other projects and wish to get closer to my children," he said. "Maybe I will open a school in Curitiba to give the opportunity to students and friends and pass them my experiences of fighting as a coach.

Anderson Silva has 4 fights remaining on his UFC contract including the UFC 101 matchup with Forrest Griffin.  So provided this is true, Silva may be able to fight one more time in 2009. Which would leave 2 more MMA fights in 2010, which means the fight with RJJ couldn't take place until at least the end of 2010 or early 2011 at the earliest.  Anderson Silva has gone from one of the most heralded fighters in MMA, to one of the most criticized after his last two fights.  Would you be interested in watching a RJJ/Anderson Silva boxing match if it happened a year or so from now?

UFC 101: Declaration coverage